I can't get more than 1/4 tank of gas in. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OJ1988 · 03-15-2006, 01:24 PM

Well, I have finally started driving my old beater truck. I have got gas 3 times now, and have not been able to get more than 1/4 tank in. I have tried holding the pump at different angles and such, but it will literally backflow out the filler neck a small bit.

I have tried different gas stations too.

I can not get more than 1/4 tank in it.

Could my gauge be off? How would I be able to tell?

I know other people say they have a hard time getting gas in these trucks too, but they can't all be this bad.

86 GMG · 03-15-2006, 03:51 PM

i have never had any problems filling my tanks in fact my truck really like to get filled up with gas and a hole lot of it, i wonder if my be your vent for the tank is pluged up or something to that effect. had this truck been change fron step side to fleet b/c the filler necks are diffrent i think? hope this helps in some kinda way

OJ1988 · 03-15-2006, 05:04 PM

Nope, its a factory stock fleetside. How could I check the vent?

A buddy of mine has an 84 and he said he has to hold the gas pump at a slight angle to get gas in his.

I also remember my dad had an 84 and he had to make sure the truck was sitting downhill to get gas in it.

1974gmc · 03-15-2006, 05:39 PM

sounds like the gauge is off to me, i had the same problem at one time but my gauge doesnt work at all

86 GMG · 03-15-2006, 06:05 PM

the filler neck has two hoses one about a two inch diameter and one thats maybe 3/4 of an inch both are clamped like a radiator hose un clamp remove from truck and poke a piece wire through if nothing but wire come through no clog. but my concern after reading the tread again is has this truck been sitting if so the float could be stuck or the gauge is stuck sound like you have some trouble shooting to do best luck!

f.monroe · 03-15-2006, 06:14 PM

Fill a 5 gallon gas can and put it in the bed . Run the truck until it runs out and see how long that takes . Frank

swb85 · 03-15-2006, 06:34 PM

You better take that gas can inside with you everywhere you go with the price of gas these days!!

Somebody will snatch that up quick!!

RUST · 03-16-2006, 08:59 PM

I can fill my tank up, but I have to play with the pump handle at different angles to get it not to drip out.

jimfulco · 03-20-2006, 11:35 PM

These things are famous for gas gauge problems. Run it until it's out, then see how much will go in it.

79BIG10 · 03-21-2006, 12:23 AM

Same problem here. The problem I found is that the new style filler spout has a automatic shutoff whenever the fuel has enough backpressure. This is created due to the fuel flowing at a high rate and the neck and opening not being able to bleed it off fast enough. Think of it this way- Take a small funned with a long neck on it and fill it full with liquid. If you keep filling it at a certain flow then it will overflow. But if you can keep it flowing at a certain rate the funnel will be able to handle it.

Two ways I've fixed this is to not depress the lever the whole way but aloow it to flow 3/4 of the amount out. Also if that doesn't help pull the spout out a bit more to where it's just in there enough. This will help allow the flow to not hit the backflow check valve and flow better. Watch this though because on some stations this has been known to prevent the valve from stopping so it's best to watch it.

Another question to help diagnose- Does your other tank register when it's full? If it doesn't then sounds like you have a gauge issue.

84slopwaggin · 03-21-2006, 01:12 AM

Yep mine too I have to cock the nozzle at the 3:00 position so it doesn't spill back onto the truck.

OJ1988 · 03-23-2006, 01:12 PM

Well, turns out the tank was full.

I pulled off the filler neck to check it, and the tank has a full tank of gas.

So either my sending unit is bad, or my gauge is bad.

I know the sending unit has an ohm range,m 0-90 I think, and I can test that, but what about the gauge? How do I check that?

79BIG10 · 03-23-2006, 03:15 PM

Do you have two tanks or just the one?

OJ1988 · 03-23-2006, 04:23 PM

Just one tank, drivers side

79BIG10 · 03-23-2006, 07:36 PM

Take a OHM meter and with the ignition turned on check the amount going to the gauge. If it reads 90ohms or so when full then it's the gauge. If not then it's the wiring/sending unit.

boxrodz · 03-23-2006, 11:15 PM

OJ-
Follow this and see if it helps.

http://67-72chevytrucks.com/vboard/s...d.php?t=190455

Good luck.

86-C10-V6 · 03-29-2006, 02:01 PM

When the guage reads 1/4 tank all the time it is a good indication of a bad calibration resistor or a bad connection to the calibration resistor on the back of the guage.
If you remove the guage, on the back you will see a white ceramic block held by two press nuts. This white block is the calibration resistor. Remove the nuts and the resistor and clean the contact areas of the resistor with a pencil eraser until the surface is shiny copper.
Check the resistor with an ohm meter, should be 90 ohms. If the resistor is open then you must replace it, or replace the whole guage.
Re-assemble and re-install
Hope this helps.

03-15-2006, 01:24 PM	#1
OJ1988 Just a car guy Join Date: Feb 2006 Location: New Washington, IN Posts: 991	I can't get more than 1/4 tank of gas in. Well, I have finally started driving my old beater truck. I have got gas 3 times now, and have not been able to get more than 1/4 tank in. I have tried holding the pump at different angles and such, but it will literally backflow out the filler neck a small bit. I have tried different gas stations too. I can not get more than 1/4 tank in it. Could my gauge be off? How would I be able to tell? I know other people say they have a hard time getting gas in these trucks too, but they can't all be this bad.

03-15-2006, 03:51 PM	#2
86 GMG Registered User Join Date: Apr 2005 Location: Tulsa Oklahoma Posts: 943	Re: I can't get more than 1/4 tank of gas in. i have never had any problems filling my tanks in fact my truck really like to get filled up with gas and a hole lot of it, i wonder if my be your vent for the tank is pluged up or something to that effect. had this truck been change fron step side to fleet b/c the filler necks are diffrent i think? hope this helps in some kinda way __________________ square body trucks an addiction or an investment either way they consume all my extra time and money

03-15-2006, 05:04 PM	#3
OJ1988 Just a car guy Join Date: Feb 2006 Location: New Washington, IN Posts: 991	Re: I can't get more than 1/4 tank of gas in. Nope, its a factory stock fleetside. How could I check the vent? A buddy of mine has an 84 and he said he has to hold the gas pump at a slight angle to get gas in his. I also remember my dad had an 84 and he had to make sure the truck was sitting downhill to get gas in it.

03-15-2006, 05:39 PM	#4
1974gmc In Progress Join Date: Feb 2005 Location: Kamloops, BC, Canada Posts: 312	Re: I can't get more than 1/4 tank of gas in. sounds like the gauge is off to me, i had the same problem at one time but my gauge doesnt work at all __________________ 1993 Chevrolet K2500 454 4L80E 1974 GMC 1/2t 2wd Stepside 305 auto sold 1985 Ford Mustang GT 5.0 5spd

03-15-2006, 06:05 PM	#5
86 GMG Registered User Join Date: Apr 2005 Location: Tulsa Oklahoma Posts: 943	Re: I can't get more than 1/4 tank of gas in. the filler neck has two hoses one about a two inch diameter and one thats maybe 3/4 of an inch both are clamped like a radiator hose un clamp remove from truck and poke a piece wire through if nothing but wire come through no clog. but my concern after reading the tread again is has this truck been sitting if so the float could be stuck or the gauge is stuck sound like you have some trouble shooting to do best luck! __________________ square body trucks an addiction or an investment either way they consume all my extra time and money

03-15-2006, 06:14 PM	#6
f.monroe Senior Member Join Date: May 2004 Location: Caldwell,Tx. Posts: 3,648	Re: I can't get more than 1/4 tank of gas in. Fill a 5 gallon gas can and put it in the bed . Run the truck until it runs out and see how long that takes . Frank __________________ Born and proudly residing in a Red State !

03-15-2006, 06:34 PM	#7
swb85 On a budget like Fred Sanford Join Date: Oct 2005 Location: Topeka, KS Posts: 2,031	Re: I can't get more than 1/4 tank of gas in. You better take that gas can inside with you everywhere you go with the price of gas these days!! Somebody will snatch that up quick!! __________________ '85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD

03-16-2006, 08:59 PM	#8
RUST Registered User Join Date: Nov 2004 Location: Roanoke, AL Posts: 18	Re: I can't get more than 1/4 tank of gas in. I can fill my tank up, but I have to play with the pump handle at different angles to get it not to drip out.

03-20-2006, 11:35 PM	#9
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Re: I can't get more than 1/4 tank of gas in. These things are famous for gas gauge problems. Run it until it's out, then see how much will go in it.

03-21-2006, 12:23 AM	#10
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,775	Re: I can't get more than 1/4 tank of gas in. Same problem here. The problem I found is that the new style filler spout has a automatic shutoff whenever the fuel has enough backpressure. This is created due to the fuel flowing at a high rate and the neck and opening not being able to bleed it off fast enough. Think of it this way- Take a small funned with a long neck on it and fill it full with liquid. If you keep filling it at a certain flow then it will overflow. But if you can keep it flowing at a certain rate the funnel will be able to handle it. Two ways I've fixed this is to not depress the lever the whole way but aloow it to flow 3/4 of the amount out. Also if that doesn't help pull the spout out a bit more to where it's just in there enough. This will help allow the flow to not hit the backflow check valve and flow better. Watch this though because on some stations this has been known to prevent the valve from stopping so it's best to watch it. Another question to help diagnose- Does your other tank register when it's full? If it doesn't then sounds like you have a gauge issue. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

03-21-2006, 01:12 AM	#11
84slopwaggin Registered User Join Date: Apr 2005 Location: Ar Posts: 558	Re: I can't get more than 1/4 tank of gas in. Yep mine too I have to cock the nozzle at the 3:00 position so it doesn't spill back onto the truck.

03-23-2006, 01:12 PM	#12
OJ1988 Just a car guy Join Date: Feb 2006 Location: New Washington, IN Posts: 991	Re: I can't get more than 1/4 tank of gas in. Well, turns out the tank was full. I pulled off the filler neck to check it, and the tank has a full tank of gas. So either my sending unit is bad, or my gauge is bad. I know the sending unit has an ohm range,m 0-90 I think, and I can test that, but what about the gauge? How do I check that?

03-23-2006, 03:15 PM	#13
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,775	Re: I can't get more than 1/4 tank of gas in. Do you have two tanks or just the one? __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

03-23-2006, 04:23 PM	#14
OJ1988 Just a car guy Join Date: Feb 2006 Location: New Washington, IN Posts: 991	Re: I can't get more than 1/4 tank of gas in. Just one tank, drivers side

03-23-2006, 07:36 PM	#15
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,775	Re: I can't get more than 1/4 tank of gas in. Take a OHM meter and with the ignition turned on check the amount going to the gauge. If it reads 90ohms or so when full then it's the gauge. If not then it's the wiring/sending unit. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson



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03-23-2006, 11:15 PM	#16
boxrodz Until Seventy Times Seven Join Date: Feb 2005 Location: Rocky Mountain Front Range Posts: 1,301	Re: I can't get more than 1/4 tank of gas in. OJ- Follow this and see if it helps. http://67-72chevytrucks.com/vboard/s...d.php?t=190455 Good luck. __________________ boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin...

03-29-2006, 02:01 PM	#17
86-C10-V6 Shadetree Mechanic Join Date: Oct 2002 Location: Youngsville, NC Posts: 100	Re: I can't get more than 1/4 tank of gas in. When the guage reads 1/4 tank all the time it is a good indication of a bad calibration resistor or a bad connection to the calibration resistor on the back of the guage. If you remove the guage, on the back you will see a white ceramic block held by two press nuts. This white block is the calibration resistor. Remove the nuts and the resistor and clean the contact areas of the resistor with a pencil eraser until the surface is shiny copper. Check the resistor with an ohm meter, should be 90 ohms. If the resistor is open then you must replace it, or replace the whole guage. Re-assemble and re-install Hope this helps. __________________ Dave M. (Hacksaw) 86 C10 Scottsdale LWB, 4.3L, Edelbrock 1904, K&N, 700R4, 3.08 Auburn Performance 89 GMC S-15 Extended Cab 4x4, 4.3L, FI 98 K1500 Xcab, 5.7L, 3.43 Gov-Lok

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